Got a 5 hour flight but only an hour or two worth of battery left on your gadgets? Depending on your airline, you may have a power outlet or USB port in your seat. Here's how to find out which planes have some extra juice to give.

Of course, to avoid this problem, you should always charge up your gadgets before you leave. If you use them in the airport, try to grab an outlet to stay charged—bringing a power strip with you will help a lot (and make you some friends along the way). A good external battery pack can go a long way, too. However, if you need an outlet, many airlines offer options, so just like we did with Wi-Fi, let's take a look at some of the most popular US airlines and what they offer.

Delta: For domestic flights, you'll find power outlets only in First Class on select 737 and 757 aircraft, and all 767-300 aircraft. USB ports, however, are available in all seats on 737-700, 737-800, 757-200, 767-300, 767-400ER, and 777-200ER and LR aircraft that feature Delta on Demand. For international flights, Delta has 110 volt power outlets in all BusinessElite seats in A330, 747-400, 757, 767-300ER, 767-400ER, and 777 aircraft, as well as in the first 10 rows of Economy Class on A330, 767-400ER and 777 aircraft and select 757 and 767-300ER aircraft.

US Airways: There are 110V AC ports in Envoy and First Class seats only on the 757-200, 767, 330-200, and 330-300 aircraft. The 330-300 also has 15V DC ports in economy seats, for which you'll need an adapter. The 330-200 include USB ports in every seat, and the 330-300 has USB ports in Envoy seats only.

United Airlines: You'll find 110V power outlets in premium seating only on 747-400 aircraft, though power outlets are coming to United Economy in 2013-2014. International fliers will find 110V power outlets on some 737-800 and 757-300 aircraft.

American Airlines: American has power on most of their planes, though some are DC outlets (like the ones in your car) instead of traditional AC power and may require an adapter—check out the link for more information. First and Business Class seats have outlets at every seat, while the main cabin has shared outlets between seats in "select rows" of the plane. Exceptions include the 737-800 aircraft, which has shared power in all rows, and the 777-300 aircraft, which also has AC and USB power at every seat.

Air Canada: Most, if not all, Air Canada aircraft have a 110V power outlet as well as a USB port for charging smaller gadgets.

JetBlue: According to JetBlue's custome rservice department, they will have in-seat power ports accessible from all seats on their new Airbus A321 aircraft, which we begin taking delivery of this year. The power ports will be internationally-compatible, have a separate USB input, and do not require an adapter. Each customer in our new Mint Experience, JetBlue’s take on the premium cabin and offered on select A321s, will have access to two power ports.

This isn't an exhaustive list, and includes the most up to date information that we could find. When we could find info on a given airline's web site, we went with that—but if an airline didn't have info, we checked SeatGuru's database. If you have any corrections (with a source to back it up), let us know and we'll tweak the list!